A Holley-Edelbrock debate
Here's what I've learned about how an automatic choke is supposed to work. You'll have to investigate whether the carbs you've got has all the features.
Initial Choke position: This is where the plate sits when the engine off. Its the maximum restriction to the carb entry.
Qualified Choke position: Plate position immediately upon starting.
* It's opened by manifold vacuum.
* The amount it opens is usually adjusted by increasing or decreasing the spring force on a vacuum diaphram.
* Usually the linkage is such that the qualified position is based on the initial position, not independent.
* It does not effect the throttle fast idle position.
Fast idle cam has two or three steps. In warmer weather the cam's linkage to the choke should rotate it off the upper step(s) pretty quick.
* There may be a way to have the choke 80% open and still have the cam rotated so the throttle is on the second step.
Some carbs have internal vacuum source connection to the choke. They may or may not have a means of adjustment if its internally connected. Some carbs don't have any vacuum source. I think the only solution for them is set the choke for the running position and use pump shot from working the throttle to get it rich enough to fire off.
My own preference is for the choke bimetal to be getting heat from the intake since the intake's temperature is what matters. But that's too complicated for aftermarket carbs so that's not a realistic choice in most cases.
So the thing usually missing from an aftermarket carb choke is a means to directly relate to the temperature of the engine and intake manifold. This a factroy Motorcraft 2150 for an AMC 360 but the concepts are the same.
Instead of piping heat up to the choke bimetal, Chrysler usually linked to the bimetal coil, which was placed in the intake manifold.
from the Chrysler Tech pamphlets.
pamphlet here: More About Carburetors (Session 223) from the Master Technician's Service Conference
Here's what I've learned about how an automatic choke is supposed to work. You'll have to investigate whether the carbs you've got has all the features.
Initial Choke position: This is where the plate sits when the engine off. Its the maximum restriction to the carb entry.
Qualified Choke position: Plate position immediately upon starting.
* It's opened by manifold vacuum.
* The amount it opens is usually adjusted by increasing or decreasing the spring force on a vacuum diaphram.
* Usually the linkage is such that the qualified position is based on the initial position, not independent.
* It does not effect the throttle fast idle position.
Fast idle cam has two or three steps. In warmer weather the cam's linkage to the choke should rotate it off the upper step(s) pretty quick.
* There may be a way to have the choke 80% open and still have the cam rotated so the throttle is on the second step.
Some carbs have internal vacuum source connection to the choke. They may or may not have a means of adjustment if its internally connected. Some carbs don't have any vacuum source. I think the only solution for them is set the choke for the running position and use pump shot from working the throttle to get it rich enough to fire off.
My own preference is for the choke bimetal to be getting heat from the intake since the intake's temperature is what matters. But that's too complicated for aftermarket carbs so that's not a realistic choice in most cases.
So the thing usually missing from an aftermarket carb choke is a means to directly relate to the temperature of the engine and intake manifold. This a factroy Motorcraft 2150 for an AMC 360 but the concepts are the same.
Instead of piping heat up to the choke bimetal, Chrysler usually linked to the bimetal coil, which was placed in the intake manifold.
from the Chrysler Tech pamphlets.
pamphlet here: More About Carburetors (Session 223) from the Master Technician's Service Conference
